The present invention relates generally to inkjet printing mechanisms, and more particularly to an electrical interconnect cleaning system that cleans ink residue from a portion of an inkjet cartridge upon removal from the printing mechanism to prevent short circuiting of the interconnect conductors across the conductive ink residue.
Inkjet printing mechanisms use cartridges, often called xe2x80x9cpens,xe2x80x9d which eject drops of liquid colorant, referred to generally herein as xe2x80x9cink,xe2x80x9d onto a page. Each pen has a printhead formed with very small nozzles through which the ink drops are fired. To print an image, the printhead is propelled back and forth across the page, ejecting drops of ink in a desired pattern as it moves. The particular ink ejection mechanism within the printhead may take on a variety of different forms known to those skilled in the art, such as those using piezo-electric or thermal printhead technology. For instance, two earlier thermal ink ejection mechanisms are shown in U.S. Pat. Nos. 5,278,584 and 4,683,481. In a thermal system, a barrier layer containing ink channels and vaporization chambers is located between a nozzle orifice plate and a substrate layer. This substrate layer typically contains linear arrays of heater elements, such as resistors, which are energized to heat ink within the vaporization chambers. Upon heating, an ink droplet is ejected from a nozzle associated with the energized resistor. By selectively energizing the resistors as the printhead moves across the page, the ink is expelled in a pattern on the print media to form a desired image (e.g., picture, chart or text).
To clean and protect the printhead, typically a xe2x80x9cservice station xe2x80x9d mechanism is supported by the printer chassis so the printhead can be moved over the station for maintenance. For storage, or during non-printing periods, the service stations usually include a capping system which substantially seals the printhead nozzles from contaminants and drying. Some caps are also designed to facilitate priming, such as by being, connected to a pumping unit that draws a vacuum on the printhead. During operation, clogs in the printhead are periodically cleared by firing a number of drops of ink through each of the nozzles in a process known as xe2x80x9cspitting,xe2x80x9d with the waste ink being collected in a xe2x80x9cspittoonxe2x80x9d reservoir portion of the service station. After spitting, uncapping, or occasionally during printing, most service stations have an elastomeric wiper that wipes the printhead surface to remove ink residue, as well as any paper dust or other debris that has collected on the printhead. The wiping action is usually achieved through relative motion of the printhead and wiper, for instance by moving the printhead across the wiper, by moving the wiper across the printhead, or by moving both the printhead and the wiper.
To improve the clarity and contrast of the printed image, recent research has focused on improving the ink itself. To provide quicker, more waterfast printing with darker blacks and more vivid colors, pigment-based inks have been developed. These pigment-based inks have a higher solid content than the earlier dye-based inks, which results in a higher optical density for the new inks. Both types of ink dry quickly, which allows inkjet printing mechanisms to form high quality images on readily available and economical plain paper, as well as on recently developed specialty coated papers, transparencies, fabric and other media.
As the inkjet industry investigates new printhead designs, the tendency is toward using permanent or semi-permanent printheads in what is known in the industry as an xe2x80x9coff-axisxe2x80x9d printer. In an off-axis system, the printheads carry only a small ink supply across the printzone, with this supply being replenished through tubing that delivers ink from an xe2x80x9coff-axisxe2x80x9d stationary reservoir placed at a remote stationary, location within the printer. Since these permanent or semi-permanent printheads carry only a small ink supply, they may be physically more narrow than their predecessors, the replaceable cartridges. Narrower printheads lead to a narrower printing mechanism, which has a smaller xe2x80x9cfootprint,xe2x80x9d so less desktop space is needed to house the printing mechanism during use. Narrower printheads are usually smaller and lighter, so smaller carriages, bearings, and drive motors may be used, leading to a more economical printing unit for consumers.
There are a variety of advantages associated with these off-axis printing systems, but the permanent or semi-permanent nature of the printheads requires special considerations for servicing, particularly when wiping ink residue from the printheads, which must be done without any appreciable wear that could decrease printhead life. To accomplish this objective, use of an ink solvent has been proposed. In this proposed system, the ink solvent, a polyethylene glycol (xe2x80x9cPEGxe2x80x9d) compound is stored in a porous medium having an applicator portion that applies the solvent to the printhead wiper. The wiper moves across the applicator to collect PEG, which is then wiped across the printhead to dissolve accumulated ink residue and to deposit a non-stick coating of PEG on the printhead face to retard further collection of ink residue. The wiper then moves across a rigid plastic scraper to remove dissolved ink residue and dirtied PEG from the wiper before beginning the next wiping stroke. The PEG fluid also acts as a lubricant, so the rubbing action of the wiper does not unnecessarily wear the printhead.
During printing and spitting, some small ink droplets may become airborne within the printer, forming what is known as xe2x80x9cink aerosol.xe2x80x9d Unfortunately, this ink aerosol often lands in undesirable locations on the inkjet cartridge that are not normally cleaned by the printhead service station. For example, this ink aerosol may collect along a portion of the cartridge exterior next to the electrical interconnect that sends the firing signals to the printhead. Moreover, the process of wiping the printhead often deposits ink on this portion of the cartridge adjacent the electrical interconnect. Beyond leaving the pen dirty with ink residue, unfortunately, many inkjet inks are also electrically conductive, so any ink smeared on the conductors of the electrical interconnect has the potential for causing a short circuit between the conductors. Ink residue deposited on the pen next to the electrical interconnect may be smeared on the interconnect conductors when the pen is removed, and then further smeared across the interconnect when a new pen is installed increasing the chances for a short circuit to occur.
The inkjet pens used in an off-axis system require special installation to align straight fluid transfer needles for insertion between the printer carriage and the printhead, so a portion of this installation must inherently have a linear motion. Thus, there is no practical way to avoid dragging this ink residue across the interconnect by employing any type of a rotational motion to move the soiled portion of the pen away from the interconnect. This inky interconnect problem is exacerbated in an off-axis system because the xe2x80x9cminixe2x80x9d cartridges that carry the printheads are replaced only occasionally during the useful life of the printer, so conceivably, this residue may build-up over a period of years, in contrast to a replaceable cartridge system, which requires replacement of the cartridge when empty.
Thus, it would be desirable to have a system for cleaning the portion of the cartridge adjacent the electrical interconnect to remove any of this potentially damaging ink residue, as well as any paper or dust fibers entrapped therein, to maintain printer reliability.
According to one aspect of the present invention, an electrical interconnect cleaning system is provided for removing accumulated ink residue from a non-printing exterior portion of an inkjet cartridge in an inkjet printing mechanism. The cleaning system includes a wiper and a support member. The support member supports the wiper in a position to remove the accumulated ink residue from the non-printing exterior portion of the cartridge through relative movement of the wiper and the cartridge.
According to yet another aspect of the present invention, a method is provided for cleaning ink residue from a non-printing exterior portion of an inkjet cartridge in an inkjet printing mechanism. The method includes the step of providing a wiper supported by a support member. In response to an action by a user to remove the cartridge from the printing mechanism, in a removing step, the accumulated ink residue is removed from the non-printing exterior portion of the cartridge through relative movement of the wiper and the cartridge.
According to a further aspect of the present invention, an inkjet printing mechanism may be provided with an electrical interconnect cleaning system as described above.
An overall goal of the present invention is to provide an inkjet printing mechanism which prints sharp vivid images over the life of the printhead and the printing mechanism, particularly when dispensed from an off-axis system.
Another goal of the present invention is to provide an electrical interconnect cleaning system for cleaning ink residue from a potentially harmful location on the exterior of an inkjet cartridge installed in an inkjet printing mechanism, before the cartridge is removed from the printing mechanism to provide consumers with a reliable, economical inkjet printing unit.